It's more a security problem
If you run an Exchange server you can avoid this by using trusted certificates. If you are cheap like me and use self-signed certificates then you have to accept that you'll need to do extra work and install a certificate generated by your server on your mobile device. While I do find it occasionally annoying, I only have to do it once and if I use Exchange, then those are the rules for self-signed certificates and I don't have to pay for a trusted one.